Energy-rich food flakes for fish and invertebrates and method for the production thereof

ABSTRACT

The invention relates to a homogeneous high-fat food provided in the form of food flakes, to a method for producing the same and to the use thereof for promoting the growth, the ingestion of food, and the condition of freshwater and saltwater fish and invertebrates. The inventive food flakes are used to improve resistance to stress, to prevent losses due to unfavorable keeping conditions such as high temperatures in the summer and low temperatures in the winter when keeping pond fish, and to reduce nitrogen and phosphorous excretion which promotes algae growth.

Usually, at present, fish feeds, especially for ornamental fish, arecharacterised by a relatively high protein content (about 40-50%) andamount of starch (about 16-30%) in the case of simultaneously relativelysmall energy content (about 0.5-8% fat). Such feeds can be producedindustrially without problem in forms of application usual for themaintenance of fish (feed flakes, floatable extrudates, tablets) andlead to a good growth and to a sufficient nutrition of the animals.

On the other hand, for the breeding and feeding of useful fish,energy-rich feed in the form of extrudates or pellets are increasinglyused which, besides a high protein content important for the growth,have fat contents of up to 25% (BioMar GmbH, company brochure“Fütterung/Umwelt-Ecoline”). The use of such feeds in the professionalfish breeding leads, in comparison with fat-poorer products, to lesswater-contaminating, nitrogen-containing excretion products (ammonia,nitrite, nitrate) since the energy requirement of the animals ispredominantly covered by the nitrogen-free fats. Therefore, thenitrogen-containing proteins serve the growth as broadly as possible anddo not have to be metabolised for the gaining of energy with formationof nitrogen-containing decomposition products. Furthermore, fats aresuperior to carbohydrates as carriers of energy in fish nutrition sincefish—unlike evolutionary higher standing animals—can only limitedlyutilise carbohydrates because of their metabolic characteristics.Therefore, the use of fat-rich fish feeds in the maintenance of usefulfish has not only economic but also ecological advantages due to thesaving of proteins and the smaller excretion of water-contaminatingmaterials.

Such feeds were hitherto not used for ornamental fish in the aquarium orin the garden pond since serious technological disadvantages counter thesaid advantages. The production of slowly sinking feed flakes which,because of the size of the animals in the ornamental fish nutrition, areusual, with high fat proportions was hitherto not possible on atechnical scale since fatrich feed mixtures for the production of flakesaccording to the usual processes stick on the roller driers normallyused and cannot be removed to give a comminutable foil strip.

Surprisingly, it has now been found that, with a new production process,flaked feed with high energy content in the form of fat/oil can also beproduced and thus the condition of fish can be distinctly improved.

The new process is based on the rolling out of formed bodies which canbe produced e.g. by extrusion or pelleting, to give thin feed flakesslowly sinking in water.

Thus, energy-rich feed flakes were produced with the new process andtested on typical ornamental fish for aquaria with regard to suitabilityin comparison with traditional standard feeds with low fat contents: Ina feeding experiment on two different ornamental fish species(Labidochromis caeruleus, Barbus conchonius), there was tested foreffectiveness a flaked experimental feed with high energy content (33%fat) in comparison with a control feed (7% fat) over a period of time of12 weeks in the case of a water temperature of 25° C.

The results clearly demonstrate that, in the case of the application ofthe energy-rich flake feed, the feed uptake is clearly increased and thegrowth of the fish is significantly better in comparison with thecontrol. Similar results are shown in the case of the feeding ofexperimental flakes with 18% or 23% of fat in comparison with a testdiet with 8% fat.

Therefore, having regard to these surprising new findings, theproduction and the use of fat-rich flaked feed is also advantageous forthe maintenance of ornamental fish.

Therefore, the subject of the present invention is an energy-/fat-richflake feed for fish and invertebrates, as well as the production and useof these flakes.

A flaked ornamental fish feed is preferred which, in homogeneousdistribution, contains energy in the form of 12-40% fat, preferably 12to 20% and quite especially preferably about 15 to 19% fat in the caseof a moisture content of 1 to 30%, preferably 4 to 25% and quiteespecially preferably of about 8%. In addition, this feed contains theusual basic components, such as 25-50% protein, preferably 43%, 10 to25% starch, preferably 13% and 10 to 60% N-free extract materials,preferably 20%, whereby all statements of amount are referred to theweight of the product.

For the production of energy-rich feed flakes, there can be used,according to the methods set out in the following, all commerciallyavailable liquid and solid fats and oils of animal or vegetable origin,individually or in combination (e.g. soya oil, fish oils, marine animalfats, tallow, sunflower oil, maize oil).

The energy addition in the form of fat/oil in high dosagings for flakedfeed for fish and invertebrates takes place during the mixing of theflour-formed and liquid feed components. Thus, a homogeneousdistribution is already ensured in the raw material mixture before thesubsequent extrusion or pelleting process and following rolling out togive flakes.

In the case of the production of extrudates, the weighed out recipecomponents are homogeneously mixed in a mixer with the necessary amountsof energy in the form of fat/oil and extruded. Thereby, for example,first 330 kg of energy-rich raw material mixture are extruded with abarrel extruder speed of 60-98%, preferably 75%, and a temperature atthe meal introduction region of 40-160° C., preferably 75° C., and inthe nozzle head of 40-190° C., preferably 75° C., with addition of 1-100l, preferably 30 l of water per hour to give 1 to 50, preferably 2-4 mmlong extrudates with a stick diameter of 1 to 10 mm, preferably 2-4 mm.

Brought about by the geometry of the outlet nozzle of-the extruder andof the desired section length of the extrusion billet, sections areobtained with equal three-dimensional form.

Subsequently, these extrudates are rolled out directly in a cylindermill to give uniformly formed flakes with a thickness between 10 μm and5 mm and a diameter between 1 to 100 mm, which also possess an equalthree-dimensional form.

Formed bodies with substantially equal three-dimensional form suitablefor rolling out can also be obtained by. pelletisation of the fat-richraw material mixture which can subsequently be rolled out to giveuniformly formed flakes.

In the case of the production of formed bodies by means of extrusion,the temperature is reducible to <80° C.

In the case of this process, after the production no additional workingsteps, such as e.g. spraying or coating with oils/fats for the energyenrichment—as in the case of conventional pellets—are necessary.

A further subject of the invention is the use of the homogeneousfat-rich feed according to the invention for the promotion of growth,feed uptake and condition of ornamental fish in fresh and sea water, forthe improvement of the resistance against stress, for the prevention oflosses in the case of unfavourable maintenance conditions, such as hightemperatures in the summer and low temperatures in the winter in thecase of the maintenance of pond fish, as well as for the reduction ofthe nitrogen and phosphorus excretion promoting algal growth.

Summary

Homogeneous fat-rich feed in the form of feed flakes, as well as processfor the production and its use for the promotion of growth, feed uptakeand condition of fishes and invertebrates in fresh and sea water, forthe improvement of the resistance against stress, for the prevention oflosses in the case of unfavourable maintenance conditions, such as hightemperatures in the summer and low temperatures in the winter, in themaintenance of pond fish, as well as for the reduction of nitrogen andphosphorus excretion promoting algal growth.

What is claimed is:
 1. A homogenous fat-rich flake feed for fish andinvertebrates comprising uniformly formed flakes having a fat content of12 to 40% and a residual moisture content of 1 to 30%.
 2. A homogenousfat-rich feed according to claim 1, wherein the fat content is from 12to 20% and a moisture content from 4 to 25%.
 3. A homogeneous fat-richfeed according to claim 2, wherein the fat content is 18% and a moisturecontent is 8%.
 4. A homogeneous fat-rich flake fish feed for fish andinvertebrates comprising uniformly formed flakes having a fat content of12 to 40%, a residual moisture content of 1 to 30%, 25 to 50% protein,10 to 25% starch, and 10 to 60% N-free extract materials.
 5. A feedaccording to claim 4 wherein the fat content comprises liquid or solidfat/oil components.
 6. A feed according to claim 5, wherein the fat/oilcomponent is soya oil, fish oils, marine animal fats, tallow, sunfloweroil, maize oil or mixtures thereof.
 7. A process for producing fat-richfish feed flakes having a fat content of 12 to 40% and a residualmoisture of 1 to 30%, comprising the steps of homogeneously mixing therecipe components; extruding the mixture at a i.) barrel extruder speedof 60-98%; ii) a temperature in the meal introduction region of 40-160°C.; iii.) a temperature in the nozzle head of 40-190° C. while iv.)adding 1-100 l of water per hour to give 1 to 50 mm long extrudates witha stick diameter of 1 to 10 mm wherein said extrudates can besubsequently rolled out to give flakes having a thickness between 10 mmand 5 mm and a diameter between 1 mm and 100 mm.
 8. A method forpromoting growth, feed uptake and condition of ornamental fish in freshand seawater comprising applying to fresh and seawater a homogenouslyfat-rich fish feed comprising uniformly formed flakes having a fatcontent of 12 to 40% and a residual moisture of 1 to 30%.
 9. A method ofmaintaining ornamental fish in fresh and seawater comprising applying tofresh and seawater a homogenous fat-rich fish feed comprising uniformlyformed flakes having a fat content of 12 to 40% and a residual moistureof 1 to 30%.
 10. The method according to claim 9 wherein the maintenanceis the improvement of the resistance against stress.
 11. The methodaccording to claim 9 wherein the maintenance is the prevention of lossesin the case of unfavorable maintenance conditions.
 12. The methodaccording to claim 9 wherein the maintenance is the reduction ofnitrogen and phosphorous excretion promoting algal growth.